/* ===== Hanbaek Lyu — personal academic site ===== */
:root {
  --accent: #c5050c;          /* UW-Madison Badger red */
  --accent-dark: #9b0000;
  --ink: #1a1a1a;
  --muted: #5c5c5c;
  --line: #e6e6e6;
  --bg: #ffffff;
  --bg-soft: #fafafa;
  --nav-bg: rgba(255, 255, 255, 0.96);
  --maxw: 900px;
  --serif: Georgia, 'Times New Roman', Cambria, serif;
  --sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--sans);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-dark); text-decoration: underline; }

/* ===== Top navigation ===== */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--nav-bg);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--line);
}
.nav-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 60px;
  flex-wrap: wrap;
}
.brand {
  font-family: var(--serif);
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--ink);
  letter-spacing: 0.2px;
}
.brand:hover { color: var(--ink); text-decoration: none; }
.nav-links {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
}
.nav-links a {
  color: var(--muted);
  font-size: 0.92rem;
  padding: 6px 10px;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}
.nav-links a:hover { color: var(--accent); background: var(--bg-soft); text-decoration: none; }
.nav-links a.active { color: var(--accent); font-weight: 600; }

/* ===== Layout ===== */
.wrap {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 48px 24px 80px;
}

/* ===== Hero (About) ===== */
.hero {
  display: flex;
  gap: 40px;
  align-items: flex-start;
  margin-bottom: 40px;
}
.hero-photo {
  flex: 0 0 210px;
}
.hero-photo img {
  width: 210px;
  height: 260px;
  object-fit: cover;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: var(--bg-soft);
}
.hero-body { flex: 1 1 auto; min-width: 0; }
.hero h1 {
  font-family: var(--serif);
  font-size: 2.1rem;
  margin: 0 0 4px;
  letter-spacing: 0.3px;
}
.hero .title {
  color: var(--muted);
  font-size: 1.02rem;
  margin: 0 0 2px;
}
.hero .affil { color: var(--muted); font-size: 0.98rem; margin: 0; }
.hero .contact-line {
  margin-top: 14px;
  font-size: 0.95rem;
  color: var(--muted);
}
.hero .quicklinks {
  margin-top: 16px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.btn {
  display: inline-block;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 6px 14px;
  font-size: 0.9rem;
  color: var(--ink);
  background: var(--bg);
}
.btn:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }

/* ===== Sections ===== */
section { margin-bottom: 44px; }
h2 {
  font-family: var(--serif);
  font-size: 1.5rem;
  margin: 0 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent);
  display: inline-block;
}
h3 {
  font-family: var(--serif);
  font-size: 1.18rem;
  color: var(--accent-dark);
  margin: 32px 0 12px;
}
p { margin: 0 0 16px; }

/* ===== News list ===== */
.news { list-style: none; padding: 0; margin: 0; }
.news li {
  display: flex;
  gap: 14px;
  padding: 8px 0;
  border-bottom: 1px solid var(--line);
  font-size: 0.96rem;
}
.news .date {
  flex: 0 0 96px;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  font-weight: 600;
}

/* ===== Publication list ===== */
.pub-group { counter-reset: pub; }
ol.pubs {
  list-style: none;
  padding: 0;
  margin: 0;
}
ol.pubs li {
  position: relative;
  padding: 12px 0 12px 34px;
  border-bottom: 1px solid var(--line);
  font-size: 0.96rem;
}
ol.pubs li::before {
  counter-increment: pub;
  content: counter(pub);
  position: absolute;
  left: 0;
  top: 12px;
  color: var(--muted);
  font-size: 0.82rem;
  font-variant-numeric: tabular-nums;
}
.pub-title { font-weight: 600; color: var(--ink); }
.pub-venue { color: var(--muted); font-style: italic; }
.pub-links a {
  font-size: 0.85rem;
  margin-right: 2px;
}
.tag {
  display: inline-block;
  font-size: 0.72rem;
  background: var(--accent);
  color: #fff;
  padding: 1px 7px;
  border-radius: 10px;
  vertical-align: middle;
  margin-left: 6px;
}

/* ===== Simple lists (teaching) ===== */
.term-list { list-style: none; padding: 0; margin: 0; }
.term-list li {
  padding: 7px 0;
  border-bottom: 1px solid var(--line);
  font-size: 0.96rem;
}
.term-list .term {
  display: inline-block;
  min-width: 130px;
  color: var(--accent);
  font-weight: 600;
}

/* ===== People columns ===== */
.cols { columns: 2; column-gap: 40px; }
.cols li { break-inside: avoid; }
@media (max-width: 640px) { .cols { columns: 1; } }

/* ===== Footer ===== */
footer {
  border-top: 1px solid var(--line);
  background: var(--bg-soft);
  padding: 28px 24px;
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
}

/* ===== Responsive ===== */
@media (max-width: 680px) {
  body { font-size: 16px; }
  .hero { flex-direction: column; gap: 24px; align-items: center; text-align: center; }
  .hero .quicklinks { justify-content: center; }
  .hero .contact-line { text-align: center; }
  .nav-inner { justify-content: center; }
  .brand { width: 100%; text-align: center; margin-bottom: 4px; }
  .news li { flex-direction: column; gap: 2px; }
}

/* ===== Foldable program description (REU) ===== */
details.prog {
  margin: 4px 0 18px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--bg-soft);
}
details.prog summary {
  cursor: pointer;
  padding: 8px 14px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent);
  list-style: none;
  user-select: none;
}
details.prog summary::-webkit-details-marker { display: none; }
details.prog summary::before { content: "\25B8\00A0"; }         /* ▸ */
details.prog[open] summary::before { content: "\25BE\00A0"; }   /* ▾ */
details.prog .prog-body {
  padding: 2px 14px 14px;
  font-size: 0.94rem;
  line-height: 1.6;
}
details.prog .prog-body p { margin: 8px 0; }
details.prog .prog-meta {
  margin: 8px 0;
  padding-left: 0;
  list-style: none;
  color: var(--muted);
  font-size: 0.88rem;
}
details.prog .prog-meta li { padding: 1px 0; border: 0; }
details.prog .prog-meta .k { color: var(--ink); font-weight: 600; min-width: 92px; display: inline-block; }

/* ===== Research highlights ===== */
.highlight {
  display: flex;
  gap: 30px;
  align-items: center;
  margin: 0 0 40px;
}
.highlight.rev { flex-direction: row-reverse; }
.highlight .fig { flex: 0 0 46%; }
.highlight .fig img {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.highlight .fig figcaption {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 6px;
  text-align: center;
}
.highlight .txt { flex: 1 1 auto; min-width: 0; }
.highlight .txt h3 { margin-top: 0; }
.highlight .txt p { font-size: 0.96rem; }
.highlight .txt .refs { font-size: 0.85rem; color: var(--muted); }
@media (max-width: 680px) {
  .highlight, .highlight.rev { flex-direction: column; }
  .highlight .txt { order: 1; }   /* text first ... */
  .highlight .fig { order: 2; flex-basis: auto; width: 100%; }  /* ... figure below it */
}

/* ===== Top FCA banner ===== */
.topbanner {
  display: block;
  height: 60px;
  background: #000 url("../images/banner/fca_banner.png") repeat-x left center;
  background-size: auto 60px;
  image-rendering: pixelated;
}
@media (max-width: 680px) { .topbanner { height: 60px; background-size: auto 60px; } }